RFR: 7903916: JMH: Faster self-PID getters

[Aleksey Shipilev]

In current GHA, macos-aarch64 runners are extremely slow. There is about 5 second delay between the last two lines:


Tue, 17 Dec 2024 11:20:33 GMT Forking using command: [/Users/runner/hostedtoolcache/Java_Corretto_jdk/21.0.5-11.1/arm64/Contents/Home/bin/java, -XX:+UnlockDiagnosticVMOptions, -XX:+UnlockExperimentalVMOptions, -DcompilerBlackholesEnabled=true, -XX:CompileCommandFile=/var/folders/3s/b36dp_4s3wv3byw057j8bp940000gn/T/jmh8396366506527642092compilecommand, -cp, /Users/runner/work/gha-perf-test/gha-perf-test/target/test-classes:/Users/runner/work/gha-perf-test/gha-perf-test/target/classes:/Users/runner/.m2/repository/junit/junit/4.13.1/junit-4.13.1.jar:/Users/runner/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:/Users/runner/.m2/repository/org/openjdk/jmh/jmh-core/1.37/jmh-core-1.37.jar:/Users/runner/.m2/repository/net/sf/jopt-simple/jopt-simple/5.0.4/jopt-simple-5.0.4.jar:/Users/runner/.m2/repository/org/apache/commons/commons-math3/3.6.1/commons-math3-3.6.1.jar:/Users/runner/.m2/repository/org/openjdk/jmh/jmh-generator-annprocess/1.37/jmh-generator-annprocess-1.37.j
 ar:, org.openjdk.jmh.runner.ForkedMain, 127.0.0.1, 49183]
Tue, 17 Dec 2024 11:20:33 GMT # Fork: 1 of 1
Tue, 17 Dec 2024 11:20:40 GMT # Warmup Iteration   1: 1345765548.585 ops/s


I figured there is a problem in `Utils.getPID()` that ends up resolving its own hostname as part of `ManagementFactory.getRuntimeMXBean().getName()` call. We can do better and shortcut this.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jmh/pull/152/files
  Webrev: https://webrevs.openjdk.org/?repo=jmh&pr=152&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903916
  Stats: 69 lines in 5 files changed: 46 ins; 12 del; 11 mod
  Patch: https://git.openjdk.org/jmh/pull/152.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/152/head:pull/152

PR: https://git.openjdk.org/jmh/pull/152